The rocking chair is a staple of Americana that is well known to those skilled in the art of chair making. A gentle rocking motion is considered by most people to add pleasure and comfort to the otherwise ordinary act of sitting, and a number of early innovations in chair making were directed to carrying out various kinds of motion. With the advent of moving chairs that rely upon moving parts to produce a rocking motion, as opposed to a true rocking chair with its familiar arching runners, a significant degree of complexity was required to a rocking motion. Generally, a set of complicated linkages has been necessary to produce the desired motion while maintaining a sufficient degree of support for the chair.
In modern moving chairs of the general class to which the present invention is directed, the arc of motion falls mostly into one of two categories: rockers, characterized by a pivoting motion analogous to a traditional rocking chair, and gliders, to which the present invention is directed, characterized by a reciprocating, front-and-back motion that lacks a vertical or pivoting component.
Complicated linkages have proven to be suitable for providing support for gliders while enabling the gliding motion, because the complexity of the linkage permits lighter-weight materials to be used without compromising support, which in turn reduces the weight of the gliding chair unit. However, the attendant and inherent difficulty associated with a complex linkage is that the greater the number of moving parts in a machine, the greater the number of opportunities for the failure of parts. Because chairs of this type are typically quite expensive, it is highly desirable to have a gliding mechanism that is less likely to fail, even after periods of prolonged use.
In addition to the potential for breakage and failure in a complicated linkage, a complicated linkage provides more opportunities for noisy operation, because the number of joints is large, and each joint may produce noise when operating under loaded motion. The presence of a repetitive and persistent noise during the gliding operation of the chair substantially reduces the desirability of the chair, because such noise is bothersome and defeats the primary purpose of a chair of this type-relaxation. Particularly over a large number of cycles and under loaded conditions, the moving parts of a complicated linkage, even if well lubricated, still involve metal parts rubbing over other metal parts. The resulting noise is likely to force substantially higher repair and maintenance costs over the life of the chair.
One approach for resolving these issues is to substitute a living hinge, made of nylon, for the complicated linkage, in order to facilitate a gliding motion. This approach is illustrated in U.S. Pat. No. 6,120,095, the disclosure of which is incorporated herein by reference. Although the complexity of the linkage is consequently reduced by the use of a living hinge, such an approach depends upon the long-term stability of the living hinge for operability. Those skilled in the art will recognize that such dependence might be misplaced, because the constant and repetitive stress on such a hinge, which is weakened by definition, may cause the living hinge to fail catastrophically after, for instance, one million gliding cycles.
What is needed, then, is a glider mechanism that avoids the problems inherent in a complicated linkage by reducing the complexity of the linkage and by employing materials that are substantially silent during operation, but that overcomes the problems associated with the use of living hinges by employing materials of substantially greater strength and reliability.